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Factors determining prevalence of maternal antibody to
measles virus throughout infancy: a review.
Caceres VM, Strebel PM, Sutter RW.
National Immunization Program, Centers for Disease Control and Prevention,
Atlanta, GA, 30333, USA. vac5@cdc.gov
The effectiveness of vaccination
against measles, the leading cause of vaccine-preventable deaths in infants
globally, is greatly impacted by the level of maternal antibody to measles
virus (or "measles maternal antibody"; MMA) during infancy.
Variation in the prevalence of maternal antibody to measles virus between
infant populations across countries and sociodemographic strata is poorly
understood. We reviewed the literature on the prevalence of MMA, focusing on
3 principal determinants: starting level of maternal antibody, placental
transfer of maternal antibody, and rate of decay of maternal antibody after
birth. Our review identified placental transfer as an important determinant,
with greater efficiency found in studies performed in developed countries.
Placental transfer was influenced by gestational age, human immunodeficiency
virus infection, and malaria. Antibody levels in mothers varied widely
between countries, although predictably according to vaccination status
within populations. Rates of antibody decay across studies were similar.
Future studies should evaluate the utility of the cord blood level of MMA as
a predictor of vaccine efficacy in infancy; inclusion of World Health
Organization international reference sera will facilitate comparisons.
Greater understanding of the determinants of the prevalence of MMA will help
national policy makers determine the appropriate age for measles
vaccination.
Secondary measles vaccine failures identified
by measurement of IgG avidity: high occurrence among teenagers vaccinated at a
young age.
Paunio M, Hedman K, Davidkin I, Valle M, Heinonen OP, Leinikki P, Salmi A,
Peltola H.
Department of Public Health, University of Helsinki, Finland.
Failure to seroconvert (primary vaccine failure) is believed to be the
principal reason (approx. > 95%) why some vaccinees remain susceptible to
measles and is often attributed to the persistence of maternal antibodies in
children vaccinated at a young age. Avidity testing is able to separate primary
from secondary vaccine failures (waning and/or incomplete immunity), but has
not been utilized in measles epidemiology. Low-avidity (LA) and high-avidity
(HA) virus-specific IgG antibodies indicate primary and secondary failure,
respectively. Measles vaccine failures (n = 142; mean age 10.1 years, range
2-22 years) from an outbreak in 1988-9 in Finland were tested for measles-virus
IgG avidity using a protein denaturating EIA. Severity of measles was recorded
in 89 failures and 169 non-vaccinees (mean age 16.2 years, range 2-22 years).
The patients with HA antibodies (n = 28) tended to have clinically mild measles
and rapid IgG response. Among failures vaccinated at < 12, 12-15 and > 15
months of age with single doses of Schwarz-strain vaccine in the 1970s, 50 (95%
CI 1-99), 36 (CI 16-56) and 25% (CI 8-42) had HA antibodies, respectively. When
a single measles, mumps and rubella (MMR) vaccine had been given after 1982 at
15 months of age, only 7% (CI 0-14) showed HA antibodies. Omitting re-vaccinees
and those vaccinated at < 15 months, Schwarz-strain recipients had 3.6 (CI
1.1-11.5) higher occurrence of HA responses compared to MMR recipients. Apart
from one municipality, where even re-vaccinees had high risk of primary
infection, 89% (CI 69 to approximately 100) of the infected re-vaccinees had an
HA response. Secondary measles-vaccine failures are more common than was more
previously thought, particularly among individuals vaccinated in early life,
long ago, and among re-vaccinees. Waning immunity even among individuals
vaccinated after 15 months of age, without the boosting effect of natural
infections should be considered a relevant possibility in future planning of
vaccination against measles.
Successful vaccine-induced seroconversion by
single-dose immunization in the presence of measles virus-specific maternal
antibodies.
Schlereth B, Rose JK, Buonocore L, ter Meulen V, Niewiesk S.
Institute of Virology and Immunobiology, University of Wuerzburg, 97078
Wurzburg, Germany.
In humans, maternal antibodies inhibit successful immunization against measles,
because they interfere with vaccine-induced seroconversion. We have
investigated this problem using the cotton rat model (Sigmodon hispidus). As in
humans, passively transferred antibodies inhibit the induction of measles virus
(MV)-neutralizing antibodies and protection after immunization with MV. In
contrast, a recombinant vesicular stomatitis virus (VSV) expressing the MV
hemagglutinin (VSV-H) induces high titers of neutralizing antibodies to MV in
the presence of MV-specific antibodies. The induction of neutralizing
antibodies increased with increasing virus dose, and all doses gave good
protection from subsequent challenge with MV. Induction of antibodies by VSV-H
was observed in the presence of passively transferred human or cotton rat
antibodies, which were used as the models of maternal antibodies. Because MV
hemagglutinin is not a functional part of the VSV-H envelope, MV-specific
antibodies only slightly inhibit VSV-H replication in vitro. This dissociation
of function and antigenicity is probably key to the induction of a neutralizing
antibody in the presence of a maternal antibody.
Influence of maternal antibodies on vaccine
responses: inhibition of antibody but not T cell responses allows successful
early prime-boost strategies in mice.
Siegrist CA, Barrios C, Martinez X, Brandt C, Berney M, Cordova M, Kovarik
J, Lambert PH.
W.H.O. Collaborating Center for Neonatal Vaccinology, Department of Pathology,
University of Geneva Medical School, Switzerland.
Claire-Anne.Siegrist@medecine.unige.ch
The transfer of maternal antibodies to the offspring and their inhibitory
effects on active infant immunization is an important factor hampering the use
of certain vaccines, such as measles or respiratory syncytial virus vaccine, in
early infancy. The resulting delay in protection by conventional or novel
vaccines may have significant public health consequences. To define
immunization approaches which may circumvent this phenomenon, experiments were
set up to further elucidate its immunological bases. The influence of maternal
antibodies on antibody and T cell responses to measles hemagglutinin (MV-HA)
were analyzed following MV-HA immunization of pups born to immune or control
BALB/c mothers using four different antigen delivery systems: live or
inactivated conventional measles vaccine, a live recombinant canarypox vector
and a DNA vaccine. High levels (> 5 log10) of maternal anti-HA antibodies
totally inhibited antibody responses to each of the vaccine constructs, whereas
normal antibody responses were elicited in presence of lower titers of maternal
antibodies. However, even high titers of maternal antibodies affected neither
the induction of vaccine-specific Th1/Th2 responses, as assessed by
proliferation and levels of IFN-gamma and IL-5 production, nor CTL responses in
infant mice. On the basis of these unaltered T cell responses, very early
priming and boosting (at 1 and 3 weeks of age, respectively) with live measles
vaccine allowed to circumvent maternal antibody inhibition of antibody
responses in pups of immune mothers. This was confirmed in another immunization
model (tetanus toxoid). It suggests that effective vaccine responses may be
obtained earlier in presence of maternal antibodies through the use of
appropriate immunization strategies using conventional or novel vaccines for
early priming.
Loss maternally derived measles immunity in Argentinian
infants.
Nates SV, Giordano MO, Medeot SI, Martinez LC, Baudagna AM, Naretto E,
Garrido P, De Wolff CD.
Instituto de Virologia Dr. J. M. Vanella, Facultad de Ciencias Medicas,
Universidad Nacional de Cordoba, Ciudad Universitaria, Argentina. snates@cmefcm.uncor.edu
BACKGROUND: Measles immunization of children at 1 year of age with a single
dose of the current vaccine has successfully reduced measles incidence in
Argentina. However, the optimal
schedule of measles vaccination of young infants would balance the risk of
early loss of maternal antibody in the majority of infants with the risk of
primary vaccine failure because of passive measles immunity. This
study is the first to document a significant association between loss of
passive measles antibody and age among infants born in 1995 and 1996 in
Cordoba City, Argentina. METHODS: This is a seroprevalence study of 340
infants to investigate the duration of transplacentally derived measles
antibody, assayed by a neutralization test, during the first 8 months of age
in Cordoba City, Argentina. RESULTS: The proportion with detectable
neutralizing measles antibodies decreased from 85% at 1 month of age to 8%
at 8 months of age. The simple logistic model with age (in weeks) as the
only variable showed that the decline in the proportion of infants with a
positive antibody titer was sharpest during the second and fifth months of
age (6.6 and 6.8% per week during a 4-week period, respectively).
CONCLUSIONS: These findings suggest that 80% of infants are susceptible to
measles infection for at least 3 months before routine immunization at 12
months of age.
Maternal measles antibody decay in rural Bangladeshi
infants--implications for vaccination schedules.
de Francisco A, Hall AJ, Unicomb L, Chakraborty J, Yunus M, Sack RB.
International Centre for Diarrhoeal Diseases Research, Bangladesh (ICDDR,
B). andres@icddrb.org
Considerable numbers of measles cases occur below the target age for
vaccination in the Indian sub-continent. The
immunogenicity of measles vaccine in infancy is dependent on the rate of
decay in maternal antibody since this antibody interferes with vaccine
induced seroconversion. This study investigated maternal antibody
decay in a rural population in Bangladesh and evaluated possible risk
factors for early decay. Measles antibodies were assessed using both ELISA
and Plaque Reduction Neutralization (PRN) test in 330 infant-mother pairs in
a cross-sectional survey. PRN was more sensitive method than ELISA for
determining antibody levels. Antibody levels decreased rapidly in infants
with increasing age. By the age of 5 months, 67% (28/42) infants had
practically no protective antibody left (30 mIU ml-1 or below). Only 12%
infants at 5 months of age, and 5% at 8 months, had levels greater than 120
mIU ml-1--stated to 'protect' children. Multiple regression showed that
maternal age was the only variable associated with the level of antibody
(maternal weight, height and MUAC were not associated), decreasing by 1.06
mIU ml-1 for each year of age (P = 0.002). Infant's antibody concentration
decreased with age by an average 2 mIU mL-1 for every month of life (P <
0.0001), and was determined by the maternal antibody concentration (P <
0.0001) (child's length, weight, MUAC, mother's gestational age and parity
were not associated). The relatively rapid antibody decay suggests that the
target age for measles vaccination might be reduced. Further, as the cohort
of vaccinated mothers enters reproductive age in Bangladesh, a more rapid
decay of antibody may be expected in future generations of Bangladeshi
children. The information presented here suggests that a formal trial of
standard measles vaccine at younger ages is justified in this population as
it could confer considerable benefit in reducing infant measles.
Protective immunity in macaques vaccinated with live
attenuated, recombinant, and subunit measles vaccines in the presence of
passively acquired antibodies.
van Binnendijk RS, Poelen MC, van Amerongen G, de Vries P, Osterhaus AD.
Department of Virology, Erasmus University, Rotterdam, Netherlands.
The presence of maternal antibodies
is one of the main causes of measles vaccine failure. To evaluate the
interference of passively acquired antibodies with vaccine efficacy,
macaques (n = 16) were vaccinated with live attenuated measles vaccine in
the presence or absence of passively acquired measles virus-specific monkey
serum antibodies. As little as 0.1 IU of virus-neutralizing antibody/mL of
serum abrogated the induction of specific serum IgM, IgG, and
virus-neutralizing antibodies. This effect was also demonstrated in monkeys
vaccinated with live recombinant vaccinia virus expressing the hemagglutinin
and fusion proteins of measles virus but not in monkeys vaccinated with the
same proteins incorporated into immune-stimulating complexes. All of the
monkeys vaccinated in the presence of virus-neutralizing antibodies (n = 9)
were still largely protected from intratracheal challenge with wild type
virus. This protection is probably mediated by the observed specific T
lymphocyte responses.
PMID: 9041322 [PubMed - indexed for MEDLINE]
Can J Public Health 1996 Mar-Apr;87(2):97-100
Measles immunization strategy: measles
antibody response following MMR II vaccination of children at one year of age.
Ratnam S, West R, Gadag V, Burris J.
Newfoundland Public Health Laboratory, Department of Health, Faculty of
Medicine, Memorial University of Newfoundland, St. John's.
Measles antibody levels were determined by the plaque reduction neutralization
(PRN) test in 580 one-year-old children before vaccination and four to six
weeks after MMR II vaccination. Fifty-one (8.8%) had maternally derived measles
antibody at prevaccination, and this was more common among children of women
born before 1967 (10.6%) vs. 4.3%; p < 0.01). Among those with maternal
antibody, only 22 (43.1%) responded with a protective PRN titre of over 120, in
contrast to 463 (87.5%) of the 529 without maternal antibody at prevaccination
(p < 0.0001). Also, the geometric mean titre was significantly lower for the
former (114.1 vs. 378.5; p < 0.0001). Overall, 15 (2.6%) of the 580 children
had no antibody response after vaccination, and a further 80 (13.8%) had a
subprotective response (PRN titre < 120). This lack of response could not be
attributed entirely to the presence of maternal measles antibody at the time of
vaccination. The MMR II vaccine may not be sufficiently immunogenic in inducing
adequate measles antibody response after a single dose given at one year of
age.
Epidemiology Research Unit, Johannesburg, South Africa.
Where immunization campaigns locally eliminate measles, it will be important to
identify the vaccination policy most likely to prevent future epidemics. The
optimum age for vaccination depends on the rate of decline of maternal
antibody, because the presence of antibody reduces vaccine efficacy. The first
part of this paper contains a quantitative reappraisal of the data on antibody
decline and seroconversion rates by age. The decline in maternal antibody
protection follows delayed exponentials, with delays of 2-4 months, and
subsequent half-lives of 1-2 months. Using this result in an analytical
mathematical model we find that the optimal age to administer a single dose of
vaccine to children, which is independent of vaccine coverage, lies within the
range 11-19 months. We also show that, where the optimal age cannot be met, it
is better to err towards late rather than early vaccination. There are
therefore two reasons why developing countries, which presently vaccinate
during infancy because measles transmission rates are high should eventually
switch to the second year of life. The possible gains from two-dose vaccination
schedules are explored with respect to both coverage and efficacy. A two-dose
schedule will be beneficial, in principle, only when there is a need to
increase net vaccine efficacy, after coverage has been maximized with a
one-dose schedule.
Questioning the level of efficacy of the
measles vaccine in use in Zimbabwe.
Marufu T, Siziya S, Manyame B, Xaba E, Silape-Marufu Z, Zimbizi P, Ruwodo C,
Mason E, Matchaba-Hove RB, Mudyarabikwa O.
University of Zimbabwe Medical School, Department of Community Medicine,
Harare, Zimbabwe.
A prospective study was carried out between 1987 and 1989 in the City of Gweru
(Zimbabwe) to assess the efficacy of the measles vaccine. The vaccine efficacy
assessment was carried out on an epidemiological basis by relating measles
transmission in the vaccinated and unvaccinated children aged 10 to 23 months.
Measles cases were identified on the basis of a standard case definition and
data on occurrence of measles cases was collected through an active
surveillance system. Efficacies of 73 pc, 82 pc and 77 pc were calculated for
the years 1987, 1988 and 1989 respectively. Over the three year period mean
efficacy was found to be 77 pc (95 pc confidence interval 75 to 79 pc). The
vaccine efficacies found in this study were lower than 85 pc which is the
officially accepted efficacy of the measles vaccine that is in use in Zimbabwe. The low vaccine efficacy found in this study is attributed to the fact that the
measles vaccine is applied (at nine months of age) when probably 10 to 20 pc of
children still have prenatally acquired maternal antibodies. It is suggested
that further studies be carried out in Zimbabwe to enable the country to define
the way forward.
Immunization Division, Centers for Disease Control, Atlanta, GA 30333.
WHO's Expanded Programme on Immunization has significantly helped to reduce
global morbidity and mortality from measles. Recently, some African countries
with high vaccine coverage levels have reported measles outbreaks in children
above the current target age group for immunization. Outbreaks such as these
are to be expected, unless close to 100% of the population are immunized with a
vaccine which is 100% effective. Success of an immunization programme requires
identification of the distribution and ages of susceptible children and
reduction of their concentration throughout the community. Priority should be
given to urban and densely populated rural areas. In large urban areas, high
coverage of infants must be achieved soon after the age at which they lose
their maternal antibodies and become susceptible. This will be facilitated by
the introduction of high-dose measles vaccines which can be given at 6 months
of age. Where measles incidence is increasing among children aged over 2 years,
immunization of older children may be considered during contacts with the
health care system, or at primary school entry, if this does not divert
resources from immunization of younger children. Health workers should be
informed of the predicted changes in measles epidemiology following
immunization. The collection, analysis and use of data on measles (vaccine
coverage, morbidity and mortality) should be improved at all levels of the
health care system in order to monitor the immunization programme's overall
impact, identify pockets of low coverage, and allow early detection of and
response to measles outbreaks.
[The transmission of maternal measles antibodies to
newborn infants in the Ivory Coast]
[Article in French]
Rey JL, Lhuillier M, Dem M, Soro B, Saki Z, Davis CE.
Service d'Epidemiologie-Institut National de la Sante Publique, Abidjan Cote
d'Ivoire.
Authors studied the disappearance of mothers measles antibodies among 286
babies from Ivory Coast 250 of which were living in Adzope, a town with
30,000 inhabitants at 100 km up North from Abidjan and the 36 other babies
in Abidjan. The study of antibodies by IHA showed a higher serum incidence
rate of mother antibodies among 4 months aged babies in Abidjan. The
more sensitive study of antibodies by the Mann serum neutralisation, shows
that when 6 months aged, 60% babies from Adzope still have antibodies and
when 10 months aged, none of the babies is positive. Serum
negativation is late compared to Brazzaville when antibodies level is lower.
[Anti-measles antibodies in the first 2 years
of life]
[Article in Spanish]
Echevarria JM, Sainz C, Monton JL, Gonzalez F, Crespo E, Morales E, Cortes
M, Taracena B, Najera R.
In order to achieve a better understanding of the epidemiology of measles in Spain
to foster vaccination policy in our country, we have conducted a serological
survey of measles antibodies in children between birth and two years of life in
the urban population of Madrid. Authors have established the rate at which
maternal antibodies are lost in these children below 15 months of life. The
results indicate that, in general maternal antibodies have already disappeared
at 9 months. Vaccination can thus be indicated around this age.
Christopher PJ, MacDonald PA, Murphy AM, Buckley PR.
We detail aspects of measles immunization programmes in several countries.
Live measles vaccine has been available in Australia for 16 years, yet, in
1981, there were outbreaks of measles in the State of New South Wales
(population 5 200 000) which led to 2200 admissions to hospital and five
deaths. In response to complaints of "vaccine failure", a survey
determined that 22.5% of children with measles seen by general practitioners
and 10.3% of those admitted to hospitals had been previously immunized.
There was no evidence of waning immunity, and noparticular batch of vaccine
was implicated. The vaccine failures
are attributed in part to failure of seroconversion in some recipients when
immunized at 12 months of age as a result of interference by
transplacentally acquired antibodies. As more of the susceptible
population is vaccinated, there will be fewer cases of measles, but among
these cases will be an increasing proportion of cases occurring in
previously vaccinated individuals. The equation to calculate this expected
proportion of "vaccine failures" is given. We support the measures
to increase immunization compliance.
The optimal age for vaccination against measles in an
Asiatic city, Taipei, Taiwan: reduction of vaccine induced titre by residual
transplacental antibody.
Lee YL, Black FL, Chen CL, Wu CL, Berman LL.
Children vaccinated when aged between six and thirteen months against
measles in Taipei showed a high frequency of response, similar to that
reported from Nairobi, Kenya and contrasting with analogous data for the
USA. The age for optimal protection against measles mortality by a single
dose of vaccine in this group of children is nine months. Maternal
antibody exerted a negative effect on measles antibody titre in vaccinees
beyond the age at which it blocked the response so that the infants
of mothers with the higher titres themselves had lower titres. A separate
effect of immunological immaturity on titre of the response could not be
demonstrated in children over six months of age.
Nearly every measles infection results in well-recognized clinical disease. In
nonimmunized populations almost every child will get measles early in life. The
universality of the disease in nonimmunized communities, particularly those in
the developing world, has led to a more or less passive acceptance of measles
as an unavoidable risk of early life. The clinical spectrum of measles ranges
from a mild, self-limiting illness to a fatal disease. Conditions encountered
mainly in the developing world, e.g., unfavorable nutrition, high risk of
concurrent infection, and inadequate case management -- particularly at home --
favor the development of complications and adverse outcome. Conversely, good
clinical management of an otherwise healthy child, a situation seen mostly in
the developed world, greatly influences the course of the disease. Hence many
in the medical profession believe that measles is a mild disease except among
populations living under particularly unfavorable conditions. Measles vaccine
is effective in preventing disease in the individual and in controlling it in
the community if it is given at the critical age when maternal antibodies wane
and the risk of natural infection increases sharply and if a high immunization
rate is maintained in the target population. The experience with immunization,
particularly in sub-saharan Africa, is rewarding: mothers who had previously
accepted measles as an unavoidable risk clamour for immunization of their
children once its effectiveness has been demonstrated. No reason exists for
measles to claim its present toll of morbidity and mortality. With extension of
the Expanded Programme on Immunization of the World Health Organization, the
impact of measles should progressively decline.
Measles vaccine failure. A survey of causes and means of
prevention.
Hayden GF.
From the article: "In
the early 1960's, it was believed that transplacentally-acquired antibody
did not persist much beyond 6 months of age. Hence, many children were
vaccinated before 1 year of age in accordance with early
recommendations. In the mid-1960's, however, maternal antibody was
detected in some infants as late as 11 months of age. Vaccination
before 1 years was then implicated as a contributing cause of vaccine
failure. More recently, maternal antibody was detected in some infants
as late as 12 months of age, using a sensitive virus neutralization assay."
The influence of maternally derived antibody
on the efficacy of further attenuated measles vaccine.
Stewien KE, Barbosa V, de Lima OS, Osiro K.
The natural decline of passively acquired maternal antibody titers and the
influence of these antibodies on the efficacy of live, further attenuated
measles vaccine were studied in 7 to 12 month old infants.
Hemagglutination-inhibition (HI) antibody titers were determined in the pre-
and postvaccination sera. HI antibodies at low titers were detected in 20 (46%)
of the 43 infants investigated, in five of six infants at seven months and two
of nine infants at 12 months of age. The serological conversion rate following
vaccination of the infants exhibiting transplacental maternal antibody was as
low as 38%, in contrast with 100% sero-conversion of the infants without
measurable antibodies of maternal origin. HI antibody titers were low in the
infants seven to nine months of age, reflecting poor antibody responses to the
administered vaccine. For the 12 month old infants the geometrical mean
antibody titer was 1 : 52. It is concluded that transplacental maternal
antibody, even at low concentration, inhibits induction of HI antibody in the
vaccinees and therefore measles vaccination must be initiated after 12 months
of age in order to achieve successful immunization of the children. Infants who
receive the vaccine before their first birthday have to be revaccinated at or
after 15 months of age.
As a result of a large outbreak of measles, measles hemagglutination
inhibition (HI) titers were measured in 465 immunized children. Titers of
less than 1:4 were found in 14.6% of children immunized at 12 months of age
as compared to 5.2% of those immunized at 13 months of age or later. Measles
antibody titers were higher in the mothers of seronegative children who had
been immunized at 11 or 12 months of age than in the mothers of seroposotive
children. Measles HI titers of 1:4 or more were present in 94% of
children immunized at 13 months of age or later between 1962 and 1964. The
findings suggest that vaccine failure and not waning antibody accounts for
the majority of titers of less than 1:4 in immunized children.
Reimmunization programs should be considered for those who were immunized
before 13 months of age.
Persistence of maternal antibody in infants
beyond 12 months: mechanism of measles vaccine failure.
Albrecht P, Ennis FA, Saltzman EJ, Krugman S.
A serologic study was made in 34 children immunized against measles at the age
of 12 months. Using a sensitive virus neutralization test, it was found that
many of the children had pre-existing maternal antibody to measles virus.
Children with high pre-existing antibody titers failed to seroconvert. Children
with lower pre-existing antibody titers seroconverted, but the resulting
antibody titer was significantly lower than in children without pre-existing
antibody titer. The results of this study demonstrate a probably mechanism for
measles vaccine failure in 12-month-old children and support the recommendation
of the Public Health Service Advisory Committee on Immunization Practices to
postpone measles vaccination to 15 months of age.
Measles (rubeola) susceptibility among elementary
schoolchildren.
Kalis JM, Quie PG, Balfour HH Jr.
Measles (rubeola) immunity among 479 elementary schoolchildren from suburban
Minneapolis was serologically surveyed in December 1971. Of the 479
children, 25 (5.2%) had hemagglutination-inhibition (HI) titers less than 2.
These children were considered susceptible to measles. For the 233 immunized
children with no measles history, 13 (5.6%) had rubeola HI titers less than
2 while 5 (5.1%) of the 98 youngsters with a history of clinical measles had
rubeola HI titers less than 2. Of the 454 immune children, 73 (16%) had
measles HI titers between 2 and 8. These findings confirm durable immunity
and a low rate of vaccine failure following live attenuated measles
vaccination but demonstrate the importance of testing sera beginning at a
dilution of 2 in order to detect children with low antibody levels. This
survey also suggests that maternal antibody interferes with the active
immune response in youngsters immunized when less than 1 year of age because
this group of children had significantly lower geometric mean titers and
significantly more susceptibles than the children immunized when greater
than or minus 2 years.
"A foolish faith in authority is the worst enemy of truth."
-- Albert Einstein, letter to a friend, 1901
"I know of no safe depository of the ultimate powers of the society but the people themselves, and if we think them not enlightened enough to exercise control with a wholesome discretion, the remedy is not to take it from them, but to inform their discretion by education."
-- Thomas Jefferson, letter to William C. Jarvis, September 28, 1820
"What's the point of vaccination if it doesn't protect you from the unvaccinated?"
-- Sandy Gottstein
"Who gets to decide what the greater good is and how many will be sacrificed to it?"
Books,
Books,